Waterford — An independent nuclear power safety expert said this week that up to 40 workers at the Millstone Power Station should receive special training in a cooling system used during plant shutdowns that malfunctioned at Unit 2 on Oct. 4.

A valve stuck in the open position that caused the problem was not properly diagnosed or closed by the four-person crew manning that system for more than three hours, resulting in a leak of 16,570 gallons of reactor cooling water.

Once they realized the valve was stuck, they shut it in about 10 minutes, stopping the coolant loss.

The event occurred while Unit 2 was being shut down for a refueling and maintenance outage.

Last week, the Nuclear Regulatory Commission announced that an inspection of the incident found three “very low safety significance” violations had occurred, the lowest of the four categories of severity used by the agency.

Plant owner Dominion began a corrective action program with the NRC.

This week, David Lochbaum, director of the Nuclear Safety Project for the Union of Concerned Scientists, a nonprofit watchdog group, said that he concluded after an analysis of the incident that a gap in training was the root cause, rather than a lack of skills on the part of the four-person crew overseeing the cooling system that day.

“This wasn’t just the result of one person or a few people having a bad day,” he said. “The procedures and the training they got just wasn’t that good. It’s not clear to me that if any other crew faced the same situation the outcome would have been different.”

Lochbaum said the lessons learned from the incident, which he characterized as a relatively “small misstep” but one that still needs to be taken seriously, should be the basis for training sessions for all workers in all shifts at both operating units at the power station who handle the shutdown cooling system.

That would total about 40 workers, he said.

The shutdown cooling system must be used any time a plant is powered down for a scheduled refueling or unexpectedly for an unplanned circumstance.

“There were a number of other independent safety systems operating, so there was no potential for the reactor core to be damaged by overheating because of this incident,” Lochbaum said. “The safety net was still intact.”

The crew was comprised of a shift technical advisor, a shift supervisor and two reactor operators.

Immediately after the incident, Dominion removed all four from duty and sent them for retraining and testing on procedures that should have been followed, said Don Jackson, chief of the operating branch for the NRC region that includes Connecticut.

In addition, the company ran a “just in time” training session for workers just after the incident to make them aware of what happened and what should have occurred, Jackson said.

“Dominion is feathering the lessons learned into the regular training programs for licensed operators,” he said. “It appears Dominion has taken prudent action regarding training for all the operators going forward.”

After the NRC’s special inspection concluded, Jackson said, it announced its preliminary findings in an exit meeting.

Typically, just the NRC inspectors and a few plant supervisors attend.

This time, however, Dominion requested that all shift managers from both operating units attend the meeting.

“That’s kind of unusual,” Jackson said.

The NRC will check the corrective actions taken by Dominion in response to the violations during upcoming inspections this year, Jackson added.

The violations found by the NRC were: Dominion’s failure to implement steps to stop the leak sooner; failure to conduct verification testing before the shutdown cooling system was put into service; and failure of the shift technical advisor to assess the problem and give advice on how to respond.

Lochbaum said the shift technical advisor is a position required by the NRC in response to the accident at the Three Mile Island plant in Middletown, Pa., in 1979.

“He’s somebody who was supposed to be free to look at the big picture, but instead, he was helping other workers get ready for the outage,” Lochbaum said. He said it is unclear whether the advisor was acting on the direction of a supervisor or on his own.

Jackson said the shift technical advisor was “distracted doing other duties” and that Dominion is “looking into” why that occurred.

Ken Holt, spokesman for Millstone, declined to disclose the current status of the shift technical advisor and the other three members of the crew involved in the incident.

He said the information about the incident has been disseminated throughout the Waterford plant, with Dominion’s other nuclear power plants and beyond.

“We took the lessons learned from this event and incorporated them into our training programs and shared them broadly with the rest of the Dominion fleet and the industry,” he said. “We’ve reinforced the lessons learned to ensure that all our operators understand what happened."

State Rep. Kevin Ryan, D-Montville and chairman of the Nuclear Energy Advisory Council, said Thursday that he had not seen Lochbaum’s report. The NRC's report on the incident, however, did call attention to possible training issues at Millstone, he said.

The council is a citizens group charged with overseeing plant performance.

“We’re hoping Dominion stays on track with proper training,” Ryan said.

He added that one of the most troublesome aspects of the incident was that the problem persisted for more than three hours.

“That was a glaring fact. It really struck you,” he said.

In his report, Lochbaum said there were five missed “clues” that the valve was stuck in the open position.

“It would have been nice had the operators not dismissed the numerous clues and detected the loss of coolant accident a few hours, and several tons of water, earlier,” he wrote.

For the public, Lochbaum said, the incident, while unfortunate, is actually reassuring.

Even though it did not threaten public safety, the response to the incident demonstrated that the NRC exercises strict oversight and that Dominion is attentive.

“The NRC is sending a clear message that they’re not waiting for a disaster to happen before problems are identified and taken seriously,” Lochbaum said. “How the company responds when there is a problem is a better measure of how serious it is about health and safety than that they have a completely clean site.”

j.benson@theday.com

Twitter: @BensonJudy